Conventionally, in order to impart a luxurious appearance, a platinum coat with high brightness has been formed as the outermost surface layer on an abrasion-resistant layer responsible for increasing the scratch resistance of an exterior component, a personal ornament such as eyeglasses, watch, decorative trim, a sporting good and the like. For example, in Patent Document 1, an underlying layer is formed on a base material, a titanium carbide layer is formed on the surface thereof by a dry plating method, and a decorative coat layer composed of platinum or platinum alloy is formed on the surface thereof by a dry plating method. However, the platinum layer as the outermost layer is expensive and therefore, must be thinly deposited, and the titanium carbide layer needs to be formed in a light color so as to inhibit color change upon separation of the thin platinum layer. In turn, the hardness of the titanium carbide layer is lower than the hardness of the original titanium carbide layer (by about 40%), and sufficient scratch resistance cannot be obtained.
Furthermore, when the amount of carbon in the titanium carbide layer is increased in order to increase the hardness and thereby enhance the scratch resistance, the scratch resistance may be enhanced, but the color tone turns dark. Also, when the film thickness of the titanium carbide layer as the hardened layer is increased so as to again enhance the scratch resistance, this results in separation of the film due to an increase in the film stress or generation of pitting corrosion in a corrosion, and therefore it has been difficult to deposit a film at a thickness of 1.0 μm or more.
In addition, the platinum-based coat has a problem that an allergy occurs upon contact with human skin.
Therefore, it has been proposed to use, as the outermost layer, an Mo coat exhibiting good performance in terms of brightness, color tone and low splash potential and having scratch resistance and a high-grade quality in place of the platinum-based coat. However, the Mo coat is disadvantageously low in corrosion resistance and cannot be used as it is. Also, use of a Cr coat exhibiting good performance in terms of brightness, color tone and low splash potential and having a high-grade quality has been proposed, but the Cr film has a problem that sufficient scratch resistance cannot be obtained because of low film hardness and separation in the production process is difficult because of very high corrosion resistance. Furthermore, it has been proposed to use, as the outermost layer, a Nb carbide film or a Ta carbide film each having high hardness and corrosion resistance, but these films also have a problem that the film thickness cannot be increase because of poor adherence to a base material and the brightness is slightly low.